A digital copying machine reads an image of a document on its own, processes data of the image thus read (image information) under appropriately set conditions, and reproduces the image on a sheet of paper so as to output the image in a form of a hard copy.
There is an image forming system in which the digital copying machine is connected with a plurality image input devices through communication lines so that image data sent from the image input devices are reproduced and outputted in a form of a hard copy by the digital copying machine. Such an image forming system may include, other than the digital copying machine, a facsimile machine, a personal computer, a printer, a scanner, and the like.
For example, the Japanese Publication for Laid-Open Patent Application No. 53-116834/1978 (Tokukaisho 53-116834) discloses an image forming system in which a plurality of image reading devices and a plurality of image forming devices for reproducing image data are interconnected so as to transmit information. In the foregoing image forming system, image data read by the image reading device are transmitted to the image forming device through a single control unit, and the image data are reproduced by the image forming device receiving the image data. Thus, the image data read by one certain image reading device (scanner) are transferred to one certain image forming device, and the image data are reproduced and outputted in a form of a hard copy by the image forming device.
The Japanese Examined Patent Publication No. 7-36592/1995 (Tokukohei 7-36592) discloses an image forming system in which a plurality of image forming devices each of which is equipped with an image reading device, an image processing unit, and an image forming unit are interconnected through communication means. In the foregoing image forming system, a set of image data to be reproduced is transmitted to the plural image forming devices interconnected with each other in the image forming system, so that the outputting job of the image data is allocated to the image forming devices in accordance with a set document image copy mode (copy mode), whereby the outputting of the image data in a form of a hard copy is performed by the image forming devices in parallel.
Such a conventional image forming system as described above, in producing hard copies, provides an advantage that an outputting time is reduced, since a necessary number of image forming devices are utilized and a job of producing a set number of copies is allocated to the image forming devices. However, in the case where a digital copying machine is adapted to be used as the foregoing image forming device, the following problems arise.
For example, in the case where other copying machines do not have a function for image processing now requested, an unexpected output is sometimes obtained when attempting to obtain the output in a hard copy form by utilizing the copying machines and allocating the outputting job to the copying machines. Besides, the conventional image forming system does not have means for informing an operator of a current output state, and hence, when such unexpected output is made, the operator cannot know it.
Furthermore, the greatest advantage of the output job allocation is that a job length, that is, a time for outputting operation is reduced, but this is not fully taken into consideration in the case of the conventional image forming system.